1. Field of the Invention
The present invention relates to a process for producing a patterned structure, particularly to a process for producing a structure having a nano-scale pattern by repeated imprinting operations.
2. Description of the Related Art
Known techniques for forming a fine pattern include photolithography, electron-ray exposure, X-ray exposure, and nano-imprint lithography. A photolithography technique is disclosed in U.S. Pat. No. 5,472,812; an electron-ray exposure technique is disclosed in Japanese Patent Application Laid-Open No. 2003-068618; an X-ray exposure technique is disclosed in Japanese Patent Application Publication No. 2004-296780; and a nano-imprint lithography technique is disclosed in US Patent Application Laid-Open No. 2005/064054. Such a technique for direct drawing of a pattern like the electron-ray drawing and the ion-beam drawing requires a longer time for forming a finer pattern. Therefore, fine pattern formation in mass production at a lower cost is conducted mainly through steps of preparing precisely a mask for X-ray exposure, UV-ray exposure, of press molding by direct drawing and forming a pattern collectively in a shorter time by photolithography or nano-imprint lithography.
However, in any of the above techniques, the fineness of the formed structure is limited. The electron-ray exposure technique, which is the most precise at the moment, is capable of forming single dots of 10 nm diameter, but is not capable of forming readily an arrangement of dots of this size in a dot arrangement pitch of 20 nm or less readily.
Other known processes for forming a fine structure include anodic oxidation of aluminum or a like material, and a bottom-up process by utilizing a molecular self-organization structure. The anodic oxidation of aluminum is disclosed in U.S. Patent Application Publication No. 2004/206632, and the bottom-up process for fine structure formation is disclosed in U.S. Pat. No. 6,602,620. Such methods are suitable for forming a regular periodic structure in a large area, but are not suitable for forming an arbitrary structure.